Manganese oxide ores predominantly contain manganese in the 4+ valence state and are largely insoluble in acidic media. To produce manganese chemicals and feed solutions for electrolytic manganese processes conventional practice has been to roast reduce the manganese to manganous oxide (2+ valence state) and then dissolve the manganous oxide in sulfuric acid. Sulfur dioxide has also been utilised in reductive leach processes to produce manganese sulfate. However, this technology has lacked efficiency due to the formation of manganese dithionate and manganese poly-thionate species as by products.
The manganese dioxide leaching route is considered to be relatively capital intensive, requiring either a reduction kiln to reduce the manganese prior to acid leaching or a sulfur burning plant to produce a liquefied or gaseous SO2 reductant for direct leach of the manganese dioxide. The handling of gas also inevitably means the size of the plant is increased in order to have the capacity required to treat the ore body.
Traditionally, low or zero value waste manganese ore materials resulting from the production of lump manganese ores have been deposited in tailings dams or in waste stockpiles at manganese mine sites. Such waste manganese ore materials may be the product of, for example, a Dense Medium Separation (DMS) Plant. Conventional processing of manganese ores has also involved milling of the ore to improve leaching kinetics in order to make the leach process viable. This milling process has been known to lead to fugitive dust emissions and localised contamination.
The treatment of sulfide ores results in sulfide waste materials being kept at site, in stockpiles or tailings dams. This is a significant problem for most sulfide treatment plants as there are environmental implications and liabilities, such as acid mine drainage (AMD).
The method of the present invention has as one object thereof to substantially overcome problems associated with the prior art, or to at least provide a useful alternative to those prior art methods.
The preceding discussion of the background art is intended to facilitate an understanding of the present invention only. The discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge in Australia or any other country as at the priority date of the application.
Throughout the specification and claims, unless the context requires otherwise, the word “comprise” or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.